1. Technical Field
This invention generally relates to computer systems, and more specifically relates to access in a computer database system.
2. Background Art
Database systems have been developed that allow a computer to store a large amount of information in a way that allows a user to search for and retrieve specific information in the database. For example, an insurance company may have a database that includes all of its policy holders and their current account information, including payment history, premium amount, policy number, policy type, exclusions to coverage, etc. A database system allows the insurance company to retrieve the account information for a single policy holder among the thousands and perhaps millions of policy holders in its database.
Retrieval of information from a database is typically done using queries. A query usually specifies conditions that apply to one or more columns of the database, and may specify relatively complex logical operations on multiple columns. The database is searched for records that satisfy the query, and those records are returned as the query result. A type of query that accesses the database is INSERT data. Data is typically added to the database using an INSERT. When a job inserts data into the database the database locks out access to other jobs. Contention occurs when one or more jobs attempt to access data that has been locked.
In a large data warehousing environment, real time data querying is very important. When a large number of jobs need to insert and/or access the data at the same time, contention on the database rises, and the time to make the inserts become excessive. The contention may be caused by not only the INSERT jobs but the other parts of the application that are querying and updating the data in real time from user input. In some applications, the jobs that are inserting records to the file are critical and cannot fall behind in processing the incoming data. Simply adding more jobs to make the inserts is not effective because it would merely increase the contention. Without a way to reduce database contention to improve system performance, the computer industry will continue to suffer from excessive delays in database accesses caused by contention in the database.